Walking or lifting beam assemblies or automatics for forging presses are known for use to supply workpieces in a stepwise fashion to the processing position or work station within the forging press. A control system for such a walking in German Patent No. 2 061 043 and comprises beam assembly is found having gripping devices for gripping workpieces between the walking beams when the walking beams have been closed with respect to each other in a clamping or closing movement. Once clamped upon the workpiece, the walking beams are lifted upwardly and carry the workpiece or workpieces in an advance movement for conveyance to a work station.
During the advance movement, the workpieces are maintained above the operating position for the work station. Upon reaching the work station, the walking beams are lowered to the work station and upon opening, the workpieces are released into the work station where the workpieces are forged during a predetermined operating cycle of the press stroke of a forging press. The walking beams are then returned to their initial position in their retracted or open condition.
In the prior art system, fast press stroke cycles require very fast movement of the walking beams without loss of operational accuracy. In particular, the operational phases for loading and advancing the workpieces may be very short. If heavy workpieces are to be conveyed, the mass moment of inertia of the workpieces can delay the manipulator movements for the lifting beam assembly.
A further problem of known manipulators or walking beam assemblies is related to the manipulator parts being subjected to large mechanical stresses due to considerable acceleration and slowing down of the individual moving processes. Furthermore, many undesired machine vibrations may occur during operation of the known walking beam assembly.
The construction and operation for a known walking or lifting beam assembly for a forging press is also disclosed in copending U.S. patent application Ser. No. 86,531 filed Aug. 18, 1987 now U.S. Pat. No. 4,873,860 owned by the same assignee and is hereby incorporated herein by reference in its entirety.